Trait ToSql

Source

pub trait ToSql<A, DB: Backend>: Debug {
    // Required method
    fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, DB>) -> Result;
}

Expand description

Serializes a single value to be sent to the database.

The output is sent as a bind parameter, and the data must be written in the expected format for the given backend.

When possible, implementations of this trait should prefer using an existing implementation, rather than writing to out directly. (For example, if you are implementing this for an enum, which is represented as an integer in the database, you should use i32::to_sql(x, out) instead of writing to out yourself.)

Any types which implement this trait should also #[derive(AsExpression)].

§Backend specific details

For PostgreSQL, the bytes will be sent using the binary protocol, not text.
For SQLite, all implementations should be written in terms of an existing ToSql implementation.
For MySQL, the expected bytes will depend on the return value of type_metadata for the given SQL type. See MysqlType for details.
For third party backends, consult that backend’s documentation.

§Examples

Most implementations of this trait will be defined in terms of an existing implementation.

#[repr(i32)]
#[derive(Debug, Clone, Copy, AsExpression)]
#[diesel(sql_type = Integer)]
pub enum MyEnum {
    A = 1,
    B = 2,
}

impl<DB> ToSql<Integer, DB> for MyEnum
where
    DB: Backend,
    i32: ToSql<Integer, DB>,
{
    fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, DB>) -> serialize::Result {
        match self {
            MyEnum::A => 1.to_sql(out),
            MyEnum::B => 2.to_sql(out),
        }
    }
}

Example of creating a custom type mapping based on a MySQL enum type

This is designed to reuse the SQL type definition generated by diesel-cli

pub mod sql_types {
   #[derive(diesel::sql_types::SqlType)]
   #[diesel(mysql_type(name = "Enum"))]
   pub struct PostEnum; //<- generated by diesel cli
}
#[derive(Debug, AsExpression, PartialEq, Clone)]
#[diesel(sql_type = sql_types::PostEnum)]
pub enum Post {
   FirstValue,
   SecondValue,
}

impl ToSql<sql_types::PostEnum, diesel::mysql::Mysql> for Post {
   fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, diesel::mysql::Mysql>) -> serialize::Result {
       match *self {
           // these string values need to match the labels used in your
           // enum definition in SQL. So this expects that you defined the
           /// relevant enum type as`ENUM('one', 'two')` in your `CREATE TABLE` statement
           Post::FirstValue => out.write_all(b"one")?,
           Post::SecondValue => out.write_all(b"two")?,
       }
       Ok(IsNull::No)
   }
}

Using temporary values as part of the ToSql implementation requires additional work.

Backends using RawBytesBindCollector as BindCollector copy the serialized values as part of Write implementation. This includes the Mysql and the Pg backend provided by diesel. This means existing ToSql implementations can be used even with temporary values. For these it is required to call Output::reborrow to shorten the lifetime of the Output type correspondingly.

#[repr(i32)]
#[derive(Debug, Clone, Copy, AsExpression)]
#[diesel(sql_type = Integer)]
pub enum MyEnum {
    A = 1,
    B = 2,
}

impl ToSql<Integer, diesel::pg::Pg> for MyEnum
where
    i32: ToSql<Integer, diesel::pg::Pg>,
{
    fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, diesel::pg::Pg>) -> serialize::Result {
        let v = *self as i32;
        <i32 as ToSql<Integer, diesel::pg::Pg>>::to_sql(&v, &mut out.reborrow())
    }
}

For any other backend the Output::set_value method provides a way to set the output value directly. Checkout the documentation of the corresponding BindCollector::Buffer type for provided From<T> implementations for a list of accepted types. For the Sqlite backend see SqliteBindValue.

#[repr(i32)]
#[derive(Debug, Clone, Copy, AsExpression)]
#[diesel(sql_type = Integer)]
pub enum MyEnum {
    A = 1,
    B = 2,
}

impl ToSql<Integer, diesel::sqlite::Sqlite> for MyEnum
where
    i32: ToSql<Integer, diesel::sqlite::Sqlite>,
{
    fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, diesel::sqlite::Sqlite>) -> serialize::Result {
        out.set_value(*self as i32);
        Ok(IsNull::No)
    }
}

Required Methods§

Source

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, DB>) -> Result

See the trait documentation.

Trait ToSqlCopy item path

§Backend specific details

§Examples

Required Methods§

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, DB>) -> Result

Implementations on Foreign Types§

impl ToSql<BigInt, Mysql> for i64

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Mysql>) -> Result

impl ToSql<BigInt, Pg> for i64

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<BigInt, Sqlite> for i64

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Sqlite>) -> Result

impl ToSql<Binary, Sqlite> for [u8]

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Sqlite>) -> Result

impl ToSql<Bool, Mysql> for bool

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Mysql>) -> Result

impl ToSql<Bool, Pg> for bool

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Bool, Sqlite> for bool

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Sqlite>) -> Result

impl ToSql<CChar, Pg> for u8

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Cidr, Pg> for IpNet

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Cidr, Pg> for IpNetwork

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Citext, Pg> for str

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Citext, Pg> for String

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Date, Mysql> for NaiveDate

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Mysql>) -> Result

impl ToSql<Date, Mysql> for Date

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Mysql>) -> Result

impl ToSql<Date, Pg> for NaiveDate

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Date, Pg> for Date

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Date, Sqlite> for str

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Sqlite>) -> Result

impl ToSql<Date, Sqlite> for NaiveDate

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Sqlite>) -> Result

impl ToSql<Date, Sqlite> for Date

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Sqlite>) -> Result

impl ToSql<Date, Sqlite> for String

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Sqlite>) -> Result

impl ToSql<Datetime, Mysql> for NaiveDateTime

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Mysql>) -> Result

impl ToSql<Datetime, Mysql> for OffsetDateTime

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Mysql>) -> Result

impl ToSql<Datetime, Mysql> for PrimitiveDateTime

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Mysql>) -> Result

impl ToSql<Double, Mysql> for f64

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Mysql>) -> Result

impl ToSql<Double, Pg> for f64

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Double, Sqlite> for f64

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Sqlite>) -> Result

impl ToSql<Float, Mysql> for f32

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Mysql>) -> Result

impl ToSql<Float, Pg> for f32

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Float, Sqlite> for f32

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Sqlite>) -> Result

impl ToSql<Inet, Pg> for IpNet

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Inet, Pg> for IpNetwork

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Integer, Mysql> for i32

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Mysql>) -> Result

impl ToSql<Integer, Pg> for i32

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Integer, Sqlite> for i32

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Sqlite>) -> Result

impl ToSql<Interval, Pg> for Duration

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

impl ToSql<Json, Mysql> for Value

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Mysql>) -> Result

impl ToSql<Json, Pg> for Value

fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> Result

Trait ToSql